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Wandering rough idle, stalling at stop lights, weird harmonic noise... 99 OBW


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10 replies to this topic

#1 remarcable

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Posted 04 December 2003 - 04:50 PM

To get things started here is the car:

-1999 Legacy Outback
-56,000 miles
-4EAT tranny :banghead:
-I use unleaded 87 octane fuel
-original battery, alternator, plug wires
-ECU reset last week after this started
-Unidentified minor coolant leak from behind the timing cover, has had it for over a year

I had a problem where #3 cyl was misfiring and the car was undrivable along with belching plumes of white smoke. I took it back to the mechanic. They said it was a loose vacuum hose and that had caused the plugs to become fouled. They cleaned the plugs, replaced the hose, and all was well (for $400).

It started doing it again a month later and I found that a plug boot was loose, so I popped it back on and the car was fine.

Now, this month, the car is stalling when braking to a slow stop and in neutral/park the idle fluctuates and bounces and the engine feels much rougher than usual.

Normal idle after warmup is 500rpm which I don't see. It stays around 500 for awhile then drops and bounces up to 1500 and repeats.

This problem is worse when the vehicle lights are on. The lights dim when the car is stuttering at a full stop.

The car drives fine at normal speed.

I also notice an unusual harmonic HUMMMMMMRMMMRMM noise that sounds somewhat electrical from under the hood while the car is driving and for about 2 seconds after the car is turned off. I have not been able to pinpoint the location of the sound, other than that is seems to be in the middle of the engine bay and is audible from inside the car.

Can anyone help me with this problem? I'm tired of hearing the headers go SPANG off the skidplate(stall/restart) and then have everyone around me at the intersection give me a :madder: look while I try and keep the engine alive until the light turns green.

#2 alias20035

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Posted 04 December 2003 - 05:15 PM

Originally posted by remarcable
To get things started here is the car:

-1999 Legacy Outback
-56,000 miles
-4EAT tranny :banghead:
-I use unleaded 87 octane fuel
-original battery, alternator, plug wires
-ECU reset last week after this started
-Unidentified minor coolant leak from behind the timing cover, has had it for over a year

I had a problem where #3 cyl was misfiring and the car was undrivable along with belching plumes of white smoke. I took it back to the mechanic. They said it was a loose vacuum hose and that had caused the plugs to become fouled. They cleaned the plugs, replaced the hose, and all was well (for $400).

It started doing it again a month later and I found that a plug boot was loose, so I popped it back on and the car was fine.

Now, this month, the car is stalling when braking to a slow stop and in neutral/park the idle fluctuates and bounces and the engine feels much rougher than usual.

Normal idle after warmup is 500rpm which I don't see. It stays around 500 for awhile then drops and bounces up to 1500 and repeats.

This problem is worse when the vehicle lights are on. The lights dim when the car is stuttering at a full stop.

The car drives fine at normal speed.

I also notice an unusual harmonic HUMMMMMMRMMMRMM noise that sounds somewhat electrical from under the hood while the car is driving and for about 2 seconds after the car is turned off. I have not been able to pinpoint the location of the sound, other than that is seems to be in the middle of the engine bay and is audible from inside the car.

Can anyone help me with this problem? I'm tired of hearing the headers go SPANG off the skidplate(stall/restart) and then have everyone around me at the intersection give me a :madder: look while I try and keep the engine alive until the light turns green.



Could be the following:

*head gasket (coolent seeping into cylinder when engine off/low idle) (do you have coolant loss, coolant leak, oil in coolant, bubbles in coolant, overheating, white sweet smelling exhaust?)
* bad coilpack (it usually misfires at high speed though, with ok idle)
* bad sparkplug wires
* Idle Air Control (IAC) acting up
* bad alternator (no voltage at idle)
* bad battery (it is 4+ years old, Sube batteries always die in year 4/5)

White smoke = coolant in cylinder = blown head gasket (in most cases), so I am hedging my bets on blown head gasket.

No coolant leak is minor, probably a blown head gasket or leaking water pump (could be both in your case), pull the timing covers off and check it out promptly. If the water pump goes the timing belt system could fail catostrophically.

Have the coolant system pressure tested to locate the leak, but odds are BOTH the head gaskets and water pump are gone. The hot exhaust gas has probably entered the cooling system and damaged the water pump causing it to leak.

Since you are due, change the timing belt as well (60,000 mile item?)

The EJ25 DOHC engine has a notoriously bad record for blowing head gaskets. Figure on up to $1,000 to fix this. Be sure the latest version of the head gasket is used, see this post

http://usmb.ultimate...=&threadid=8073

#3 alias20035

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Posted 04 December 2003 - 05:19 PM

You should still be covered on the 5yr/60,000 mile powertrain warranty, which will cover the head gasket..... and Idle Air Control, and some of the other items I listed.

Even if you bought the car in late 98 and are off the warranty I would go to a dealer, they may still cover this (if you can prove that the problem occured during the warranty period), sometimes they offer to pay half....

#4 remarcable

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Posted 04 December 2003 - 06:18 PM

I just changed the oil last weekend and noticed nothing unusual about it.. no milky color, no water droplets... just normal slightly used mobil 1.

I've been avoiding the local dealership since they are incompetent, deceitful, and did I mention incompetent? I've modifed the intake (snorkus removal) and I have a 2.5 stromung muffler on the car, held on by 14 gauge speaker wire in place of muffler hangars (ghetto, but effective.) They see this, they see all the dents and scratches (which all happened while the car was parked with nobody behind the wheel - hit and runs) the perma-stained underbody from the local red clay, and they assume abuse. The car has been over some rough roads and seen an autocross or two but I have in no way abused the engine and try to take very good care of it. The suspension on the other hand.... I wouldn't make a warranty claim on the suspension. I'm an honest person.

I'd also rather not drive it there (1 hour away to the nearest dealership) and have it be something like the battery or IAC.

I'll replace the battery tomorrow; it has some nasty corrosion on it I don't like and cleaning the posts works for about a week then it comes back. I even stripped the cable back some to get fresh wire, and now that too is corroded. Looks like fluffly blue salt structures.


So you think it could be something OTHER than a Headgasket Failure? It has leaked small amounts of coolant (I top off the reservoir w/ 50/50 mix every few months, it never gets too low) for about a year now.

#5 alias20035

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Posted 04 December 2003 - 08:15 PM

Originally posted by remarcable
I just changed the oil last weekend and noticed nothing unusual about it.. no milky color, no water droplets... just normal slightly used mobil 1.

I've been avoiding the local dealership since they are incompetent, deceitful, and did I mention incompetent? I've modifed the intake (snorkus removal) and I have a 2.5 stromung muffler on the car, held on by 14 gauge speaker wire in place of muffler hangars (ghetto, but effective.) They see this, they see all the dents and scratches (which all happened while the car was parked with nobody behind the wheel - hit and runs) the perma-stained underbody from the local red clay, and they assume abuse. The car has been over some rough roads and seen an autocross or two but I have in no way abused the engine and try to take very good care of it. The suspension on the other hand.... I wouldn't make a warranty claim on the suspension. I'm an honest person.

I'd also rather not drive it there (1 hour away to the nearest dealership) and have it be something like the battery or IAC.

I'll replace the battery tomorrow; it has some nasty corrosion on it I don't like and cleaning the posts works for about a week then it comes back. I even stripped the cable back some to get fresh wire, and now that too is corroded. Looks like fluffly blue salt structures.


So you think it could be something OTHER than a Headgasket Failure? It has leaked small amounts of coolant (I top off the reservoir w/ 50/50 mix every few months, it never gets too low) for about a year now.



Since you seem to know what you are doing, I would definitely pop the timing belt covers and check the water pump, and thermostat housing as well. You need to fix the coolant leak, since small leaks lead to big leaks or problems down the road.

My thought was head gasket because:

* EJ25 DOHC head gaskets suck (at least the original ones do)
* white smoke in exhaust (I have never seem a missing vacuum hose cause white smoke)
* bad running at idle (where head gasket failures typically cause the most trouble)
* hissing sound after shut down (could be coolant spraying into the cylinder when the cylinder depressurizes). There should be nothing electrical live under the hood post engine shutdown to cause a noise.

It could be coil pack or wires, but I don't think so. I would have a local garage do a cooling system pressure test and test the coolant for hydrocarbons. If the tests come up fine, you should then look elswhere.

Cars with bad electrical systems will sometimes idle roughly, but they usually won't start without being boosted as well.

#6 alias20035

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Posted 04 December 2003 - 08:18 PM

Originally posted by alias20035
Since you seem to know what you are doing, I would definitely pop the timing belt covers and check the water pump, and thermostat housing as well. You need to fix the coolant leak, since small leaks lead to big leaks or problems down the road.

My thought was head gasket because:

* EJ25 DOHC head gaskets suck (at least the original ones do)
* white smoke in exhaust (I have never seem a missing vacuum hose cause white smoke)
* bad running at idle (where head gasket failures typically cause the most trouble)
* hissing sound after shut down (could be coolant spraying into the cylinder when the cylinder depressurizes). There should be nothing electrical live under the hood post engine shutdown to cause a noise.

It could be coil pack or wires, but I don't think so. I would have a local garage do a cooling system pressure test and test the coolant for hydrocarbons. If the tests come up fine, you should then look elswhere.

Cars with bad electrical systems will sometimes idle roughly, but they usually won't start without being boosted as well.



Could the 2 second post stall electrical sound be the rad fan? If so is your car running hot? hot = blown head gasket

#7 remarcable

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Posted 04 December 2003 - 08:30 PM

Originally posted by alias20035
Could the 2 second post stall electrical sound be the rad fan? If so is your car running hot? hot = blown head gasket



No, it isn't the fans since the sound continues even with the key out of the ignition (plus I know how the fans sound). The sound very well could be coolant or another fluid being sprayed inside of the engine. This would also explain my difficulty in pinpointing it.

I have been concerned about the 2.5 headgasket issue since I first heard about it a year or two ago, and will try and find someone to do a hydrocarbon test on the coolant tomorrow.

Thanks for the replies and I suppose we'll see how the test comes up tomorrow.

Oh, in regards to temp, the idiot gauge says normal and I've never seen it rise above midway during the time I've had the car (bought w/ 48 miles on it in june 99).

#8 alias20035

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Posted 04 December 2003 - 08:44 PM

Originally posted by remarcable
No, it isn't the fans since the sound continues even with the key out of the ignition (plus I know how the fans sound). The sound very well could be coolant or another fluid being sprayed inside of the engine. This would also explain my difficulty in pinpointing it.

I have been concerned about the 2.5 headgasket issue since I first heard about it a year or two ago, and will try and find someone to do a hydrocarbon test on the coolant tomorrow.

Thanks for the replies and I suppose we'll see how the test comes up tomorrow.

Oh, in regards to temp, the idiot gauge says normal and I've never seen it rise above midway during the time I've had the car (bought w/ 48 miles on it in june 99).



You often get overheating with a blown headgasket, but in some cases you do not. If your leak is isolated to a single cylinder, it is possible that the temperature would not rise. If your mechanic has a scope he can inspect the cylinder walls through the spark plug hole, if one cylinder (or a bank of cylinders) is much cleaner than the others, coolant has likely gotten in and cleaned them (blown head gasket). Usually at this point you would have milky oil though.

In addition to the hydrocarbon test, definitely take the timing covers off and inspect the water pump and timing belt assembly. You should also check the timing belt tensioner and belt for signs of wear.

You need to find that coolant leak!!! A leaking water pump is a very dangerous thing to have for a long period.

#9 alias20035

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Posted 04 December 2003 - 08:52 PM

I forgot to add:

Also have the mechanic check the vacuum hose routing and EGR if so equipped. Is it possible that the vacuum hoses were connected wrong when fixed a while back?

Your spark plug wire that comes loose should be easily fixed by compressing the connector ring so it grabs the spark plug firmly. You should also use spark plug boot grease to seal the wire to the plug and wire to the coilpack.

I had one wire on my 93 Legacy that was alwasy popping off, I eventually used a small amount of RTV sealant (or something like it) to hold the wire in the head of the engine, problem solved... My problem was with brand new wires....

The hissing sound could also be air trapped in the cooling system, or the rad drawing coolant back in from the overflow.

#10 remarcable

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Posted 09 December 2003 - 07:29 PM

I have yet to take the car to a mechanic, however I have ordered the following parts:

-Water pump + gasket
-Timing Belt
-Thermostat + gasket
-new struts and springs (yay!)
-new rear brakes
-new bulbs all around

My theory on the noises:

-Droning at idle and probably while driving
*Failing water pump possibly from headgasket failure, possibly normal wear.

-High pressure hiss sound that continues when the car is turned off (sometimes for up to several minutes)
*Air trapped in coolant system OR coolant being sprayed into engine

As soon as I get the parts in from 1stsubaruparts.com (good prices, good service) I'll be taking it to a local mechanic to get the timing belt, water pump, and thermostat replaced. I didn't order a new tensioner because I'm hoping the old one will still be fine at 56k miles.

I have examined the coolant and it smells like coolant. I can't smell any gasoline or combustion-related odors in the overflow tank, and I have never seen bubbles in the overflow tank even after 'spirited' driving.

Even if my headgaskets are OK, should I still expect to have them fail? Should I order the latest revision headgasket and have it installed as a preventative measure?

I'm going to read up on procedures in my Haynes manual and check out a few things like the AIC, PCV, and whatever else isn't too in-depth for tonight. I might even take pictures if I have questions.

Thanks for all the assistance!

EDIT- PCV valve checks fine, but the EGR doesn't move as freely as I think it should.

It isn't seized, but the movement isn't smooth and requires some force.

#11 intrigueing

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Posted 10 December 2003 - 08:32 AM

The drone could be the waterpump going south, however when I removed the snorcus, I got the exact noise you are speaking of, I put the snorcus back in and the noise disappeared - it could be slightly heard when the car was on, but was most noticable just after the car was turned off.




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